Direct and indirect effects of sea spray geoengineering and the role of injected particle size

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réchauffement climatique, eau de mer, sel, nuage

Nuages au dessus de San Franscisco © JUSTIN SULLIVAN / GETTY IMAGES NORTH AMERICA / AFP

Climate-aerosol model ECHAM5.5-HAM2 was used to investigate how geoengineering with artificial sea salt emissions would affect marine clouds and the Earth’s radiative balance. Prognostic cloud droplet number concentration and interaction of aerosol particles with clouds and radiation were calculated explicitly, thus making this the first time that aerosol direct effects of sea spray geoengineering are considered. When a wind speed dependent baseline geoengineering flux was applied over all oceans (total annual emissions 443.9 Tg), we predicted a radiative flux perturbation (RFP) of ?5.1 W m?2, which is enough to counteract warming from doubled CO2 concentration. When the baseline flux was limited to three persistent stratocumulus regions (3.3% of Earth’s surface, total annual emissions 20.6 Tg), the RFP was ?0.8 Wm?2 resulting mainly from a 74–80% increase in cloud droplet number concentration and a 2.5–4.4 percentage point increase in cloud cover.

Journal of Geophysical Research Atmospheres

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